Many times it is desirable to interconnect a semiconductor device, either in leaded form or as a semiconductor die, to a printed circuit board while providing a carrier structure for the semiconductor device or die to serve as an interim carrier to facilitate mounting the semiconductor device or die to the printed circuit board. In the field of semiconductor die carriers, various different types of semiconductor carriers have been proposed including LID's (leadless inverted devices). In a LID, a semiconductor die is first mounted in a carrier, and then the carrier is inverted and the carrier has bonding pads that subsequently mate with bonding pad areas on a printed circuit board. Generally these LID carriers are complex to construct and the mounting and assembly of them may not provide sufficient heat sinking capabilities for the semiconductor device.
Another method of mounting semiconductor die directly to a circuit board is by using flip chip technology in which bonding pads on the semiconductor die top surface are connected via small solder balls or bumps to solderable bonding pads on the printed circuit board. The problems inherent in such a system is that extremely close tolerances must be provided on the circuit board to facilitate the connection of the very small bonding pads on the semiconductor die to corresponding small bonding pads on the circuit board thus requiring very high resolution for conductive paths and bonding pads on the circuit board.
An interim solution to some of the structures discussed above is the providing of a semiconductor die carrier which will directly interface to the semiconductor die bonding pads, as in the case of a flip chip, but wherein subsequent connection to a much larger and more easily manufactured printed circuit board is achieved by having much larger bonding pads on the carrier connected to much larger printed circuit board bonding pads via much larger solder ball connections. These types of assemblies are generally referred to as grid ball array assemblies. In some grid ball array assemblies a semiconductor die is mounted on top of a carrier structure and electrical connections from the semiconductor device are provided to bottom side solder bumps on the carrier by means of plated through holes or other types of through hole connections in the carrier circuit board. One such technique comprises an overmolded pad array carrier structure in which the carrier actually comprises an epoxy circuit board having through hole connections. Other carriers which utilize a ceramic carrier having through hole connections are referred to as "Cerpac" carriers.
In the above type of carriers, the providing of through hole connections can add to the cost of the entire assembly. Also, there can be potential reliability problems with respect to the through hole connections unless there are stringent and costly controls on the through hole connection materials and processes. What is needed is an inexpensive, more manufacturable and reliable type of semiconductor assembly which preferably eliminates the need for through hole connections, while providing the advantages of having a carrier for a delicate semiconductor device. Preferably, such an improved carrier should also have good thermal conductivity characteristics and be able to reliably withstand large temperature variations.